Novel processing aids for natural and synthetic rubber compounds

ABSTRACT

This invention is directed to novel compositions which aid in the processing of natural and synthetic rubber by permitting the usual peptizing step of such processing to be omitted. These compositions contain salts of aromatic sulfonic acids as well as long chain (fatty) acids as essential ingredients.

BACKGROUND OF THE INVENTION

Crude natural rubber is generally quite high in viscosity and thereforedoes not mix easily and quickly with the many additives used duringprocessing. To facilitate these additions, such rubber usually issoftened by undergoing a preliminary step called mastication.

The rubber is placed into a usual mixer, such as the Banbury, and issubjected to heat and a plasticizer (peptizer), while being mixed, forseveral minutes. It is then dumped, sheeted on a roll mill and cooled.The softened rubber then undergoes the mixing step.

The use of the novel processing aids of this invention eliminate theneed for the mastication step. These compositions can be added directlyto the crude rubber in the mixing cycle along with the other additives.It is, therefore, an object of this invention to provide novel rubberprocessing compositions which will facilitate the breaking of thepolymer and thereby eliminate the need for both the mastication step andthe peptizers used therein.

The novel processing compositions of this invention have otherbeneficial effects in rubber compounding. They reduce the mixing timerequired for the rubber compounding and provide for better dispersal ofadditives than traditional methods. In addition, they lower mixingtemperatures and provide for improved flow, improved physicalproperties, improved mixing and extruding characteristics, and improvedphysical characteristics of the rubber. Hence, even the compounding ofsynthetic rubber requiring no premastication will be enhanced by the useof these formulations.

It is, therefore, a further object of this invention to provide novelrubber processing compositions which facilitate the mixing of rubbercompounds with natural and synthetic rubbers in relation to timerequirements, arrangement of schedule for the addition of variouscompounding ingredients, and the possibility of uninterrupted workingwith the mixed compound because of lower, safer dump temperatureswithout adversely affecting physical properties of said rubbercompounds.

SUMMARY OF THE INVENTION

This invention relates to novel processing aids for rubber compounding,and in particular it relates to novel compositions which eliminate theneed for a separate mastication operation and provide for improving themixing time, improving the dispersal of additives and lowering of mixingtemperatures when compounding rubber.

The novel compositions of this invention allow the mastication andmixing steps to be combined into one continuous operation because themixing time is shorter and temperatures are lower. Physical propertiesof the rubber compound are improved as the dispersion of additives isimproved providing for greater uniformity in the rubber product.

The essential components of the compositions of this invention arehomogeneous mixtures of,

1. alkali salts of aromatic sulphonic acids; the general formula forsuch sulfonic acids being ##STR1## wherein X can be either hydrogen or abranched or straight chain alkyl group having from 4 to 14 carbon atoms,the preferable alkyl group having a chain length of about 8 to 12 carbonatoms such as potassium octylbenzene sulfonate, potassium.[.n-dodecyebenzene.]. .Iadd.n-dodecylbenzene .Iaddend.sulfonate andmixtures thereof; and

2. long chain fatty acids having a maximum of about 22 carbon atoms inthe chain, such as, but not limited to, stearic acid, palmitic acid,oleic acid and mixtures of such acids. The fatty acids should be presentin amounts at least about equal to the amount of sulfonates but may bepresent in substantial excess if desired.

The above essential components usually are mixed with suitable materialsto facilitate introduction into the polymer. Such materials includeesters and ethers of aromatic alcohols, acids, etc. These additionalmaterials are preferably similar to the materials comprising thecomposition of the invention of my copending Application, Ser. No.128,549, of Mar. 26, 1971. These generally are aromatic esters,compounds with alcoholic and glycolic hydroxyl groups, potassium orsodium soaps of fats or fatty acids, metal soap of zinc, magnesium,calcium or barium, and a paraffin. Specifically, these additionalmaterials may comprise

a. From about 5 percent to about 15 percent of aromatic esters selectedfrom groups consisting of (1) diaryl- and di-alkylaryl phthalates, (2)diaryl- and alkyl-aryl mon-glycolether phthalates, (3) phthalates frompolyglycol mono-ethers of aryl and alkylaryl compounds wherein thepolyglycol chain contains from 2 to 6 ethylene oxide groups in thechain, (4) di-benzoates of glycol and propyleneglycol, and their di- andtri-mers; and (5) mixtures of the above.

b. From about 5 percent to about 30 percent of compounds with alcoholicor glycolic hydroxyl groups selected from (1) straight or branched chainaliphatic alcohols having from about 8 to 20 carbons in the chain, (2)alkyl-phenoxy ethers of glycols or polyglycols wherein the alkyl groupis limited to about 12 carbons in the chain, and the polyglycol groupingdoes not contain more than about 6 (CH₂ --CH₂ --O--) groups, (3)polypropylene glycol of about three propylene oxide groups in themolecule, and (4) mixtures of the above.

c. From about 5 percent to about 15 percent of potassium or sodium soapsmade from commercial mixtures of fats or fatty acids containing fromabout 12 to about 18 carbon atoms in the chain, said chains having onlya small degree of unsaturation, with more than 50 percent of them having18 carbon atoms in the chain.

d. From about 10 percent to about 30 percent of fatty acids having fromabout 12 to about 18 carbon atoms in the chain, said chains have only asmall degree of unsaturation, with more than 50 percent of them having18 carbon atoms in the chain.

e. From about 5 percent to about 10 percent of a metal soap where themetal is selected from the group consisting of zinc, magnesium, calcium,or barium; and the fatty acid part of the soap has from about 12 to 18carbon atoms in the chain and contains a high percentage of chains witha single double bond in the chain.

f. From about 15 percent to about 60 percent of hydrocarbons selectedfrom the group consisting of mineral oil, mineral waxes, and petrolatum,or mixtures of them.

Preferably the potassium or sodium soaps of (c) above or the fatty acidsof (d) above are compounds which have iodine values in the range ofabout 5 to about 15. The metal soaps of (e) above are more unsaturatedand have iodine values in the range of about 80 to about 95.

Typical aromatic esters of (a) above which may be used in thecompositions of this invention are Dibenzylphthalate Diphenylphthalate,Di-(2-Phenoxylethyl) Phthalate; Di-(Nonyl-phenoxyethyl) Phthalate,Di-(Nonylphenoxytetraethyleneglycol) Phthalate;Benzyldodecylphenoxyhexaethyleneglycol Phthalate;Di-Octylphenoxyhexaethyleneglycol Phthalate; DiethyleneglycolDibenzoate, Dipropyleneglycol Dibenzoate, Triethyleneglycol Dibenzoate.

Illustrative of the compounds with alcoholic or glycolic hydroxyl groupsreferred to in (b) above which may be employed are 2-Ethylhexanol, CetylAlcohol, Stearyl Alcohol, Nonylphenoxyglycol, Nonylphenoxydiglycol,Nonylphenoxytetraethyleneglycol, Dodecylhexaethyleneglycol,Dipropyleneglycol, Tripropyleneglycol.

Among the potassium or sodium soaps referred to in (c) above are sodiumand potassium soaps of hydrogenated tallow, hydrogenated oils ofvegetable or marine origin, and soaps of potassium or sodium made withfractions prepared from oils and fats, such fractions having iodinevalues from about 5 to about 15.

Typical fatty acids which may be employed are those derived fromhydrogenated tallow, hydrogenated oils of vegetable or marine origin.

Illustrative of the fatty acids part of the metal soaps referred to in(e) above are oils of vegetable origin or fractions of animal fattyacids such as red oil.

Among the petroleum jellies, mineral oils, and mineral waxes, which maybe employed in the compositions of this invention, are waxes havingmelting points of about 120° to 170° F.

However, compositions of this invention are not limited to the aboveadditional materials and any similar chemicals will suffice. Allingredients may be of technical grade and may contain varying amounts ofrelated materials, by-products, etc. The novel rubber processing aids ofthis invention can be made by melting the ingredients together, mixingand cooling, forming a waxy solid. The additional materials may be addedtogether with the sulfonic acid and fatty acid and all components heateduntil a clear melt is obtained. The alkali soaps and soaps of thebivalent metals can also be made in situ as is well known in the art,from the oxide, hydroxide or carbonate of the metal and the desiredacids or acid anhydrides followed by the evaporation or boiling off ofthe resulting water.

A preferred formulation for balance processing aids of this inventioncontains the following approximate percentages by weight of compoundswhich are typical of their class:

3 percent to 15 percent alkali salt of aromatic sulfonic acid

5 percent to 25 percent fatty acid

7 percent to 15 percent diphenylphthalate

10 percent to 20 percent Tetraethyleneglycol monononylphenolether

5 percent to 10 percent Tripropyleneglycol

5 percent to 20 percent Potassium stearate

4 percent to 10 percent Zinc Oleate

0 percent to 5 percent Cetyl alcohol

15 percent to 40 percent Petrolatum

The compositions of this invention are generally added to the rubber atthe beginning of the mixing cycle. The usual additives, such aspigments, fillers, vulcanizing agents, etc., can then be added and theentire compounding performed in one operation.

The processing aids of this invention are employed in small, buteffective amounts. It is generally added in the range of about 1 percentto about 5 percent and preferably in the range of about 2 percent toabout 4 percent, based on the total weight of the rubber material. Theymay be added to any type rubber, whether it is of a natural, syntheticor reclaimed type.

The following typical compounds and examples describe this invention andits application.

COMPOUND A

10.0 parts Potassium n-dodecylbenzenesulfonate, techn. (mixed isomers)

22.0 Parts Stearic acid, techn. rubber grade

10.0 Parts Diphenylphthalate, techn.

15.0 Parts Tetraethyleneglycol monononylphenolether, techn.

5.0 Parts Tripropyleneglycol, techn.

18.0 Parts Potassium stearate, techn.

4.0 Parts Zinc oleate, techn.

2.0 Parts Cetyl alcohol, techn.

14.0 Parts Petrolatum, N.F.

The above ingredients, were melted together and thoroughly mixed, toform a waxy solid.

COMPOUND B

3.0 parts Potassium .[.octylbenzenesulfate.]..Iadd.octylbenzenesulfonate.Iaddend., techn. (mixed isomers)

11.0 Parts Stearic acid, techn., rubber grade

9.5 Parts Diphenylphthalate, techn.

16.0 Parts Tetraethyleneglycol monononylphenolether, techn.

6.5 Parts Tripropyleneglycol, techn.

8.0 Parts Potassium stearate, techn.

9.0 Parts Zinc oleate, techn.

37.0 Parts Petrolatum, N.F.

The above ingredients were melted together and mixed thoroughly to yielda soft wavy material.

COMPOUND C

3.0 parts Potassium n-dodecylbenzenesulfonate, techn. (mixed isomers)

11.0 Parts Stearic acid, techn., rubber grade

9.5 Parts Diphenylphthalate, techn.

16.0 Parts Tetraethyleneglycol monononylphenolether, techn.

6.5 Parts Tripropylene glycol, techn.

8.0 Parts Potassium stearate, techn.

9.0 Parts Zinc oleate, techn.

37.0 Parts Petrolatum, N.F.

The above ingredients were melted together and thoroughly mixed to yielda soft waxy material.

All of the above formulations, made in accordance with this invention,were used as additives at about a 4 percent level in various natural andsynthetic rubber formulations. Results of these tests are set forthbelow.

EXAMPLE NO. 1 (NATURAL RUBBER COMPOSITION)

100.00 parts Ribbed smoked sheet No. 4

0.33 Parts Di-o-benzamidophenyl disulfide

4.00 Parts Mixture of high molecular weight sulfonic acid and mineraloils sold under tradename K-Stay G by the Vanderbilt Co.

55.00 Parts Carbon black ISAF

8.00 parts Pine tar

5.00 Parts Zinc oxide

2.50 Parts Stearic acid, rubber grade

1.00 Parts diphenylamine-acetone reaction product sold under tradenameAgerite superflex by the Vanderbilt Co.

1.00 Parts Mixture of aromatic amines sold under the tradename Ageritehypar by the Vanderbilt Co.

0.65 Parts N-oxydiethylene benzothiazole- 2 -sulfenamide

0.65 Parts N-nitrosodiphenylamine

2.50 Parts Insoluble sulfur

The optimum processing for the natural rubber compositions of ExampleNo. 1, as established by actual production runs, involved three separatemixing cycles:

PEPTIZING-MASTICATION CYCLE

1. The ribbed smoked sheet and di-o-benzamidophenyl .[.si-sulfide.]..Iadd.disulfide .Iaddend.were mixed for 7 minutes in a Banbury mixer.The dump temperature was approximately 250° F. The rubber was thenstored before further processing.

2. The peptized rubber was admixed with the other ingredients of theformula except the curatives and accelerators in a 13 minute Banburycycle. The dump temperature was approximately 280° F., too high forinclusion of the accelerators, etc. The rubber was stored for cooling.

3. To this blend the curatives of the formula were added on an openmill. Three minutes of milling were required for proper dispersion.

The total time consumed by the processing, not considering handling andstorage time, was about 23 minutes.

It was found that by omitting the peptizer in the formula of Example No.1 and introducing about 4 parts of the compositions of this inventioninto the formula, mixing could be performed in much less time and in asingle mix cycle. This afforded great savings in handling and storingthe material. These fillings are shown in the following examples:

EXAMPLE NO. 2 (NATURAL RUBBER COMPOSITION)

100.00 parts Ribbed .[.smoke.]. .Iadd.smoked .Iaddend.sheet No. 4

4.00 parts Compound A of this invention

4.00 Parts Mixture of high molecular weight sulfonic acid and mineraloils sold under the tradename K-Stay G by the Vanderbilt Co.

55.00 Parts Carbon black ISAF

8.00 parts Pine tar

5.00 Parts Zinc oxide

2.50 Parts Stearic acid, rubber grade

1.00 Parts Diphenylamine-acetone reaction product sold under tradenameAgerite superflex by the Vanderbilt Co.

1.00 Parts Mixture of aromatic amines sold under the tradename Ageritehypar by the Vanderbilt Co.

0.65 Parts N-oxydiethylene benzothiazole- 2-sulfenamide

0.65 Parts N-nitrosodiphenylamine

2.50 Parts Insoluble sulfur

The above formula was mixed in a single Banbury mix cycle taking 8minutes, dump temperature 240° F. The dispersion of ingredients asbetter than that obtained in the 3-cycle mixing of Example No. 1

EXAMPLE No. 3 (NATURAL RUBBER COMPOSITION)

100.00 parts Ribbed smoked sheet No. 4

4.00 Parts Compound B of this invention

4.00 Parts Mixture of high molecular weight sulfonic acid and mineraloils sold under the tradename K-Stay G by the Vanderbilt Co.

55.00 Parts Carbon black ISAF

8.00 parts Pine tar

5.00 Parts Zinc oxide

2.50 Parts Stearic acid, rubber grade

1.00 Parts Diphenylamine-acetone reaction product sold under tradenameAgerite superflex by the Vanderbilt Co.

1.00 Parts Mixture of aromatic amines sold under tradename Agerite hyparby the Vanderbilt Co.

0.65 Parts N-oxydiethylene benzothiazole- 2-sulfenamide

0.65 Parts N-nitrosodiphenylamine

2.50 Parts Insoluble sulfur

The composition of Example No. 3 was mixed in a single pass. The timerequired was 10 minutes, dump temperature was 255° F.

Improvements in mixing of neoprene compounds with the aid of thecompositions of this invention is illustrated by the following twoexamples:

EXAMPLE NO. 4 (NEOPRENE WHV COMPOSITION)

100.00 parts Neoprene WHV

2.00 parts Phenyl-octylphenylamine

4.00 Parts Magnesium oxide

5.00 Parts Zinc oxide

0.50 Parts Stearic acid

20.00 Parts Carbon black FEF

35.00 parts Carbon black FT

20.00 parts Calcium carbonate

0.50 Parts Trimethylthiourea

Through a series of trial runs it had been established that a 12 minuteBanbury mixing cycle was required for satisfactory dispersion of thefillers in the polymer. The dump temperature was approximately 265° F.

The above compares unfavorably with Example No. 5 containing Compound Cof this invention.

EXAMPLE NO. 5 (NEOPRENE WHV COMPOSITION)

100.00 parts Neoprene WHV

4.00 parts Compound C of this invention

2.00 Parts Phenyl-octylphenylamine

4.00 Parts Magnesium oxide

5.00 Parts Zinc oxide

0.50 Parts Stearic acid

20.00 Parts Carbon black FEF

35.00 parts Carbon black FT

20.00 parts Calcium carbonate

0.50 Parts Trimethylthiourea

After 8 minutes of mixing in a Banbury mixer, dispersion of fillers inthis polymer were better than those achieved in a 12 minute run withoutCompound C. The dump temperature was 235° F.

Examples No. 6 and No. 7 show differences in processing astyrene-butadiene (SBR) stock with and without the compositions of thisinvention.

EXAMPLE NO. 6 (SBR, CARBON FILLED COMPOSITION)

100.00 parts SBR 1500 rubber

2.00 Parts High molecular sulfonic acid - mineral oil mix sold undertradename Bondogen by the Vanderbilt Co.

5.00 Parts Zinc oxide

2.00 Parts Stearic acid, rubber grade

1.50 Parts Phenyl-octylphenylamine

50.00 Parts ISAF black

2.00 Parts Sulfur

1.50 Parts Benzothiazyldisulfide

This composition was mixed in two cycles because high mixingtemperatures did not allow the introduction of the curatives andaccelerators. The practical method was to mix the SBR, bondogen, zincoxide, stearic acid and the phenyl-octylphenylamine together with 25parts of the ISAF black. This step took 8 minutes. Later, in a secondmix cycle, the remainder of the ingredients was admixed. Time requiredwas 5 minutes, dump temperature 240° F.

EXAMPLE NO. 7 (SBR CARBON FILLED COMPOSITION)

100.00 parts SBR 1500 rubber

3.00 Parts Compound A of this invention

2.00 Parts High molecular sulfonic acid - mineral oil mix sold undertradename Bondogen by the Vanderbilt Co.

5.00 Parts Zinc oxide

2.00 Parts Stearic acid, rubber grade

1.50 Parts Phenyl-octylphenylamine

50.00 Parts ISAF black

2.00 Parts Sulfur

1.50 Parts Benzothiazyldisulfide

This was mixed in a single stage. The time required for completedispersion of ingredients was 4-1/2 minutes against a total of 13minutes for Example No. 6; the dump temperature was 220° F.

What is claimed is: .[.1. A composition of matter comprising: sulfonicacid is from 1:1 to 8.33:1..]. .[.2. A composition according to claim 1wherein the long chain fatty organic acid is stearic acid..]. .[.3. Acomposition according to claim 1 wherein the alkyl substituents havebetween 8 and 12 carbons in the chain..]. .[.4. A composition accordingto claim 1 wherein the alkali salt of the aromatic sulfonic acid isselected from the group consisting of potassium octylbenzene sulfonate,potassium n-dodecylbenzene sulfonate and mixtures thereof..].
 5. Acomposition .[.according to claim 1 to which is added.]. .Iadd.of mattercomprising:a. an alkali salt of an aromatic sulfonic acid having theformula ##STR3## wherein x is hydrogen or a branched or straight chainalkyl group having from 4 to 14 carbon atoms; b. a long chain fattyorganic acid having a maximum of about 22 carbon atoms in the chainwherein the weight ratio of said fatty acid to said sulfonic acid isfrom 1:1 to 8.33:1; and c. .Iaddend. additional materials includingaromatic esters, compounds with alcoholic and glycolic hydroxyl groups,potassium or sodium soaps of fats or fatty acids, a fatty acid, a metalsoap of zinc, magnesium, calcium or barium, and a paraffin.
 6. Acomposition according to claim 5 comprising from about 3 percent toabout 15 percent of the alkali salt of said aromatic sulfonic acid,about 5 percent to about 25 percent of said long chain fatty organicacid, about 7 percent to about 15 percent diphenylphthalate, about 10percent to about 20 percent tetraethylene glycol mono-nonylphenolether,about 5 percent to about 10 percent tripropylene glycol, about 5 percentto about 20 percent potassium stearate, about 4 percent to about 10percent zinc oleate, up to 5 percent cetyl alcohol, and about 15 percentto about 20 percent petrolatum.
 7. An improved rubber compositioncomprising a rubber base, carbon black, rubber additives wherein theimprovement comprises a small but effective amount of a compositioncomprising:a. the alkali salt of an aromatic sulfonic acid having theformula ##STR4## wherein x is hydrogen or a branched or straight chainalkyl group having from 4 to 14 carbon atoms, and b. a long chain fattyorganic acid having a maximum of about 22 carbon atoms in the chain,wherein the weight ratio of said fatty acid to said sulfonic acid isfrom 1:1 to 8.33:1, and said amount being sufficient to eliminate theneed for .[.subse-quent.]. .Iadd.subsequent .Iaddend.separatemastication of said rubber composition.
 8. A rubber compositionaccording to claim 7 wherein said amount is between about 1 percent toabout 5 percent by weight.
 9. An improved method for compounding rubbercomprising admixing rubber with an additive of the class consisting ofpigments, fillers and vulcanizing agents, wherein the improvementcomprises admixing a composition .[.according to claim 1.]..Iadd.comprising:a. an alkali salt of an aromatic sulfonic acid havingthe formula ##STR5## wherein x is hydrogen or a branched or straightchain alkyl group having from 4 to 14 carbon atoms; and b. a long chainfatty organic acid having a maximum of about 22 carbon atoms in thechain wherein the weight ratio of said fatty acid to said sulfonic acidis from 1:1 to 8.33:1 .Iaddend.with rubber at the beginning of themixing cycle prior to mastication of the rubber and no later than thetime when said rubber is admixed with said additive.
 10. A methodaccording to claim 9 wherein said composition comprises from about 3percent to about 15 percent of the alkali salt of said aromatic sulfonicacid, about 5 percent to about 25 percent of said long chain.[.(fatty).]. .Iadd.fatty .Iaddend.organic acid, about 7 percent toabout 15 percent diphenylphthalate, about 10 percent to about 20 percenttetraethylene glycol mono-nonylphenolether, about 5 percent to about 10percent tripropylene glycol, about 5 percent to about 20 percentpotassium stearate, about 4 percent to about 10 percent zinc oleate, upto 5 percent cetyl alcohol, and about 15 percent to about 20 percentpetrolatum.